Pulse signal decoder for proportional control



July 17, 1951 c. l. scr-,u--ERA PULSE SIGNAL DECODER F'OR PROPORTIONAL CONTROL 5 Sheets-Sheet l Filed April 30, 1948 July 17, 1951 c. l. scHAFER PULSE SIGNAL DECODER FOR PROPORTIONAL CONTROL 5 Sheets-Sheet 2 Filed April 30, 1948 NVENTOR. MEQ/7551( f( F? BY do /yr /VF/ m/M H l- .---L.

July 17, 1951 c. l. scHAr-'ER 2,560,600

PULSE SIGNAL DECODER EOR PROPORTIONAL CONTROL.

Filed April 30, 1948 3 Sheets-Sheet I5 "i5 El Sfm' Patented July 17, 1951 O F F l C E PULSE SIGNAL DECDER FOR PRPOR- TIUNAL CONTROL Chester I. Schafer, Dayton, Ohio Appiication April 30, 1948, Serial'No. 24,293

7 Claims.

(Cl. Z50-27) (Granted under the act of ,March .3, 1883,

amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to me of any royalty thereon.

This invention relates in general to proportional control systems and particularly to a decoding circuit for analyzing a received pulse signal containing proportional control information and producing a control effect in accordance with the information contained in the signal.

The general type of signal with which the circuit is designed to operate consists of a synchronizing pulse followed by a plurality of control pulses. Each control pulse represents a separate control and individual control means are provided at the transmitter for shifting the time position of each of the control pulses away from a neutral or median time position by an amount proportional to the displacement of the control means from its neutral position and in a direction determined by the direction in which the control means is displaced from its neutral position. At the receiving end each of the control pulses is channeled, by means of a suitable pulse selector arrangement, into a decoding circuit of the type to be described Which analyzes the time position of the received pulse with respect to its neutral or median time position and causes a mechanical or electrical control effect to follow the received pulse and to assume a position relative to its neutral position which corresponds to the time position of the received control pulse relative to its neutral or median time position. In special cases modified forms of the decoder circuit may be used with signals differing in some respects from the above described type, as will be explained.

It is accordingly the object of the invention to provide a decoding circuit capable of producing a proportional control eilect from a received pulse carrying control information in the form of a displacement from a predetermined time position.

It is a further object of the invention to provide a decoding circuit of the above described type that is adaptable to use in a multiple arrangement so that a number of proportional controls may be carried out over a single transmission channel.

Specific embodiments of the invention will be described in connection with the accompanying drawings in which Fig. 1 shows a suitable pulse selector circuit for use with the decoding circuit,

Fig. 2 shows a specific embodiment of a decodin g circuit in accordance with the invention,

Fig. 3 shows a number of graphs useful in explaining the operation of Figs. 1 and 2,

Fig. 4 shows a modification of element 32 of Fig. 2,

1GO microseconds, after the synchronizing pulse.

individual control means each displaceable to either side of a neutral or center position are provided in the transmitter for displacing each control pulse to either side of its neutral position. The arrangement is such that when the control means is in its neutral or center position the control pulse is in its neutral position and displacement of the control means from its neutral or center position causes the pulse to be displaced from its neutral position by an amount and in a direction corresponding to the amount and direction of the displacement of the control means.

Accordingly pulse 2 is in the neutral position, pulse 3 lags its neutral position by 25 microsecands and pulses 4 and 5 lead their neutral positions, as determined by the positions of the corresponding control means. For example, pulse 3 may be used to transmit right-left control information. In this case the control means may bea control stick movable to the right or left from a neutral position. Displacement of the stick to the right of neutral causes pulse 3 to be displaced to the right of its neutral position by a corresponding amount as shown in Fig. 3 (a). As will be seen the maximum permissible displacement of a pulse in this case is 50 microseconds and the limits are defined by vertical dotted lines in Fig. 3.

In order to channel the control pulses 2, 3, 4 and 5 into individual decoding circuits some form of pulse separation circuit is required. A suits able circuit for performing this function is shown era-.tor may be a multivibrator of the conventional one-cycle type and when triggered by the negative pulse produces a substantially rectangular negative pulse having a duration, in this case,

slightly greater man 450 microseconds. The negative rectangular pulse is applied to gated amplifier I and serves to block this amplifier for the duration of the pulse thus preventing control pulses 2, 3, 4 and 5 from getting through. The 450+ microsecond pulse is also applied to keyer I2 which applies a positive keying pulse of the same duration to oscillator I3 which is normally blocked. The period of this oscillator is adjusted to equal 100 microseconds, corresponding to a frequency of kilocycles per second. Application of the keying pulse to the oscillator causes it to be unblocked and to oscillate during the presence of the pulse, or for slightly more than four and one-half complete cycles. The oscillator may be a form of tuned multivibrator having a substantially rectilinear output as shown in Fig. 3 (b). The output of the oscillator is applied to differentiating circuit I4 which produces therefrom a series of sharp alternately negative and positive pulses spaced 50 microseconds apart as shown at (c). This series of pulses is in turn applied to clipper and inverter I5 which removes the negative pulses and inverts the positive pulses resulting in series of negative pulses spaced 100 microseconds apart with the rst pulse in the series occurring 50 microseconds after the synchronizing pulse I as shown at (d).

Block-s I6 through 2B represent identical trigger circuits of the Eccles-Jordan type the details of which are the same as for circuit i8 in Fig. 2. These circuits consist essentially of two amplifier tubes connected in a regenerative loop so that-the circuit has two conditions oi stability in each of which one tube is fully conductive and the other vcut orf. The circuit may be triggered from one condition of stability to the other by the yapplication of a negative pulse to the conductive tube. Whe-n such a circuit is triggered from o-ne to the other condition of stability by a first negative trigger pulse and back to the original condition of stability by a second negative trigger pulse there is developed a negative rectangular pulse at the anode of one tube and an equal positive rectangular pulse at the anode of the other tube, the duration of the pulses being equal to the time difference between the trigger pulses.

The inverted synchronizing pulse that is :applied to multivibrator li is also applied to the trigger circuit I6. Also provision is made for applying the series of pulses shown in Fig. 3 (d) and obtained from clipper and inverter I5 to each ci the trigger circuits I6 through 2G. The output of each of the trigger circuits I6 through I9 is coupled to the succeeding trigger circuit through differentiating circuits 2l through 24. The outputs of trigger circuits Il through 2d are also applied to gated amplifiers through 28, respectively. The input signal applied to gated amplifier il) is also applied to each of gated ampliners 25 through 28. Terminals ai through a4 lare connected to the outputs of differentiating circuits 2I through 2li, respectively, terminals b1 through bi are connected to the outputs of gated amplifiers 25 through 28, respectively, and terminals ci through ci are each connected to the outputs of differentiating circuits 22, 23, 24 and 29 respectively.

The operation of the circuit of Fig. l is as follows: The negative trigger pulse obtained from the inversion of synchronizing pulse I by gated amplier and inverter Il) and applied to multivibrator I I is also applied to the conductive tube in trigger circuit I6 and triggers this circuit to itsother condition of stability. After 50 microseconds the rst pulse in series (d) is applied to the other tube of circuit i6 and triggers the circuit back to its original condition of stability. This process causes the circuit i5 to generate a positive 50 microsecond pulse as shown in Fig. 3 (e). The 50 microsecond pulse is applied to differentiating circuit 2i which produces a sharp positive pulse from its leading edge and a sharp negati-ve pulse from its trailing edge, which two pulses are applied to the grid of the conductive tube in trigger circuit I7. The positive pulse has no effect on the circuit but the negative pulse triggers the circuit to its other condition oi stability where it remains until the second pulse in series (d), which is applied to the grid of the other tube in circuit i?, triggers the circuit back to its original condition of stability.v The effect of these two trigger pulses, which are microseconds apart, on circuit l? is to cause that circuit to generate a 100 microsecond positive pulse as shown in lig.'3 (1'). In a similar manner remaining trigger circuits, i8, is and 2li generate successive positive 100 microsecond pulses as shown at (g), (h), and (i), each circuit being triggered through one cycle by a negative pulse obtained from the trailing edge of the 100 microsecond pulse generated by the preceding trigger circuit and by the next occurring pulse in the train (d). The pulses generated by circuits Il through which will be termed gates, are applied 'to gated anipliers 25 through 2&3, respectively, and serve to render the amplifiers operative to pass any signal applied to their input circuits during the presence of the gate applied thereto. Since the entire input signal (a) is applied to each of the gated ampliers it is seen from Fig. 3 that control pulse 2 will be applied during the operative period oi gated ampliiier 25 and will appear at terminal b1. Similarly control pulses 3, ii and 5 `will appear at terminals b2, b3 and b4, respectively. At each of terminals ci through ci will appear the negative trigger pulse from the output of differentiating circuits 2| through 2d, respectively. At each of terminals ci through ci will appear the negative trigger pulse from the output of differentiating circuits 12:2, 23, 2li and 29. There will also appear at ter'- ininals ai through ai and ci through ci the positive pulses present in the output of the corresponding trigger circuits; however these pulses have no signiiicance as Will be seen later. Accordingly the significant trigger pulses appearing Iat terminals ai-'bi-ci through aiv-bi--ci are as shown in Fig. 3 at (j), (k), (l) and (m) respectively. It will be noted that the lirst and last puls-es in these groups of three pulses are spaced 190 microseconds apart and correspond in time to the beginning and end of the corresponding gate pulse. The control information is contained in the direction and amount of the displacement of the intermediate pulse from the midpoint of the time interval defined by the two outer pulses.

A decoding circuit constructed in Iaccordance with the principles of the invention is shown in Fig. 2. This circuit is capable of analyzing a signal of the above described type and of producinga voltage at terminals 30 having a value proportional to the displacement of the intermediate control pulse from its neutral position and a polarity corresponding to the direction of this displacement. If a mechanical control effect is desired this may be obtained by direct mechanical coupling to shaft 3 I. In explaining the operation of the circuit it is assumed that terminals r-bX-c'x are connected .to terminals ,az-bz--cz of Fig. 1 -iso that the signal shown `at (1c) in Fig. 3 .is applied to the decoding circuit. This signal is seen to `comprise two negative pulses dening an interval of v100 microseconds and an intermediate ycontrol vpulse,which `is pulse 3 of .original signalia), displaced microseconds to the right of its neutral position in the center of this interval.

The rst'negative pulse to occur in the signal (k) .is applied to the gridfof vthe left :handsection of :the dual section amplier tube of trigger circuit 32. This circuit is of the conventional Eccles-Jordan vtype l.which comprises `two ampliier-tubes connected in a regenerative loop so that the circuit has two conditions of ,stability in each of which one tube is fully conducting `and the other cut off. The application .of .a negative trigger Vpulse to the conductive tube causes a rapid switch to the other conditionof stability in which the tube to which the pulse was applied is cut off and the other tube is fully conductive. The application of a second negative `,pulse .to the second tube, which is now conductive, :causes a rapid transition back to the `iirst condition of stability with the rst'tubeiagain conductive and the second tube cut 01T, This cycle of .operation causes a positive pulse to be produced at the anode of .one tube and a negative pulse at the anode of the other tube, both pulses being of the same duration as the time interval between :the two trigger pulses. In the operation of circuits of'this type the application of a positive pulse to the grid of a conductive tube lhas no effect on the circuit. Also, due to the high negative -*bias on the grid of the non-conductive tube due to drop across the common cathode resistor caused by the space current 'of the conductive tube, the application of a positive pulse to the grid of a non-conductive tube has no effect on the circuit provided the pulse amplitude is maintained below the value required -to overcome the above mentioned bias andcause'conduction-in the tube. Hence the lpreviously mentioned positive pulses that also occur at terminals Vax and cx may be disregarded.

Therefore, assuming that the left hand amplier section of circuit 32 is initially conductive the application of the rst negative pulseof signal (1c) to the Agrid thereof through terminal ax causes this section to be cut off andthe other section to'become conductive. rIhls condition exists until the third pulse of signal (lc), which occurs 100 microseconds after the first pulse, is lapplied to the grid of the right hand Iamplifier section through terminals cx and triggers the circuit back to its initial condition of stability with the left hand section conducting and `the right hand section cut off. This process produces a 100 mlcrosecond negative pulse at the anode of the right hand section which is applied to the grids of isolating-and inverting tubes 33 and 34. The resulting 100 microsecond positive pulse 'from the output of tube 33 -is applied to rgrid 35 of gated amplier 36, and that from the output of tuber?l is similarly applied to grid 3'| of gated amplifier 38. Tube 36 is normally biased to anvinoperative condition by the negative voltage applied to ,grid vfrom potentiometer 39--40, and tube 38 is biased to an inoperative condition vin ,a ysimilar manner. The positive 10,0 lmicrosecond pulses applied to=grids 35 Aand 31 are vof sufficient amplitude toovercome this ,disabling bias-and to .place the tubes inran operative Ycondition for-the duration vof the pulse. The function .of .circuit 32 CII therefore is -to place gated .amplifiers l35 and 36in anoperative condition for the duration of the `lnput signal (k) applied to terminals ax--bx--ca The circuit defined by block `4| is an adjustable. delay circuit, the adjustable feature of which is actuated by shaft 3| so that the circuit generates a pulse the duration of vwhich is determined by the position of this shaft. The circuit must -be designed so that in the central orneutral-position of the Ashaft ,the pulse generated has a duration of 50 microseconds while for maximum lclockwise rotation of .the shaft the pulse duration is 100 microseconds and for maximum counterclockwise rotation of the shaft the pulse duration is zero. The circuit shown for accomplishing this result is known as the phantastron delay circuit and an analysis of its operation may vbe found on pages 2-58 to 2-63 of the book Principles of Radar, second edition, `1946, by the members of the staff of the Radar School, Massachusetts Institute of Technology, published by the McGraw-Hill Book Company. T-he essential features of the circuit are that a negative pulse is obtained from across cathode resistor 42 the duration vof which is determined by the initial charge of condenser y43 which is in turn determined by the initial anode voltage of tube 44. The initial anode voltage of this tube is controlled by diode and potentiometer 46, the diode having its anode connected to the anode of tube 44 and its cathode through resistor 4l` to the adjustable Contact of 'potentiometer 45. Th point of conduction of diode 45 determines the potential of -the anode of tube 44. Rotation of potentiometer 46 clockwise causes the cathode potential of diode 45 to lbe vraised thus allowing the anode potential of tube 44 to rise until tHe anode potential of the diode equals that of its cathode. Similarly counterclockwise rotation o? potentiometer 46 lowers the diode cathode potential causing the anode potential of the diode and that of tube 44 to follow. The circuit may be triggered by application of a negative pulse to the anode of tube 44 through vdiode 45. The duration of the resulting pulse developed across -resistor 42 is very nearly linearly related to the angular position of potentiometer 46, and it is this feature of the circuit that makes its use desirable in this application. However it is not necessary that a delay circuit of the above type be employed and any other suitable adjustable delay circuit, such as a one-cycle multivibrator, may be used.

The first negative pulse of signal (7c) appearing at terminal an, in addition to being applied to trigger circuit 32, is also applied to trigger circuits i8 and 49 which are identical to circuit 32, and to the delay circuit 4|. In both circuits 48 and 49 the left hand amplifier sections are initially conductive and the eiect of this pulse is to cut these sections off and to render the right hand sections conductive. The pulse also triggers delay circuit 4| causing it to generate a negative pulse having a duration proportional to the setting of shaft 3| and potentiometer 46. Since the shaft is shown in its neutral or center angular position the duration of the pulse generated in this case is 50 microseconds. The delay pulse is applied to a differentiating circuit comprising condenser 5G and resistor 5! which converts the leading and trailing edges into sharp negative and positive pulses respectively. These pulses are inverted by tube 52 and applied tothe grid of the right hand :tube section of circuit 48, the negative pulse acting Ato trigger this cirllit back to its initial condition of stability with the left hand section conductive and the right hand section cut oil. The resulting 50 microsecond positive pulse developed at the anode of the left hand section is inverted anddelayed by circuit 53 and applied to the grid 31 of tube 38 along with the 100` microsecond pulse from tube 34. The pulse from circuit 48 is also applied to a differentiating circuit comprising condenser '54 and resistors 55 and t8, the resulting sharp positive and negative pulses produced from the leading and trailing edges being applied to grid 6l of tube 36.

The intermediate control pulse of signal A(lc) is applied to terminal bx and thence to the grid of the right hand tube section of circuit 49. the case of signal (1c) this pulse occurs 75 microseconds after the negative pulse at terminal ax and acts to trigger circuit ill baci: to its initial condition of stability. The resulting 75 microsecond positive pulse generated at the anode of the left hand section is inverted and delayed by circuit Evi and applied to grid 35 of tube 36 along with the 100 microsecond pulse from tube 33. The pulse produced by circuit 49 is also applied to a differentiating circuit comprising condenser 63 and resistors B4 and 35, the resulting sharp positive and negative pulses developed from the leading and trailing edges being applied to grid 66 of tube 38.

A rectiiier comprising diode '81 and resistor 58 is connected across the output circuit of gated amplier 33 and a similar circuit comprising diode 63 and resistor lis connected across the output of gated amplifier 38. Tubes 1l and 1E have relays 13 and 14, respectively, connected in their plate circuits. The grids of these tubes are connected to the cathodes of rectiiiers 61 and t3, respectively, through low pass filters comprising condensers 15 and 15 and resistors 11 and 13. A negative voltage obtained from a potential divider composed of resistors 19 and 8U acts to charge condensers 15 and 15 and to make the grids of tubes 1l and 12 negative with respect to their cathodes by the amount of the condenser voltage. This biasingfvoltage is made sufficient to reduce the space current of tubes 1l and 12 below the threshold value for relays 13 and 11i. In the presence of an output from gated amplifier 35 and 33 a direct voltage is developed across corresponding resistor 38 or it which opposes the voltage across resistor Sil and allows condenser 15 or 15 to discharge thus raising the grid potential and anode current of corresponding tube 1l or 12 and actuating corresponding relay 13 or 1:1. Disappearance of the output signal from the gated amplifier allows the corresponding condenser to recharge and the associated relay to be de-energized.

With the signal shown in Fig. 3 (lc) applied to terminals aX-lJx-cx and shaft 3l in its neutral or center position the conditions existing in the decoding circuit are as shown in Fig. 2. For reasons explained in detail in the preceding paragraphs a negative 75 microsecond pulse and a positive 10D microsecond pulse are applied to grid 35 of tube (it. Also sharp positive and negative pulses resulting from differentiation of the 50 microsecond pulse produced by circuit 48 are applied to grid 8l of tube 3S. The negative pulse applied to grid 35 cancels the 100 microsecond positive gating pulse for 75 microseconds so that the amplifier 38 is only operative during the last microseconds of the 100 microsecond interval. Therefore, since the negative pulse applied to Vthat shown at (7'). pulse applied to grid 6,6 of tube 38 occurs at 50 8. grid 6l occurs at 50 microseconds, this pulse does not get through and relay 13 is not energized.l Considering gated amplier 38, however,l a microsecond negative pulse and a 100 microsecond positive pulse are applied to grid 31 While sharp positive and negative pulses resulting from differentiation of the microsecond pulse produced by circuit i9 are applied to grid 6'6. Since tube 38 is therefore operative for the last 50 microseconds of the 100 inicrosecond interval and since the negative pulse on grid occurs at 7-5 microseconds, this pulse gets through. A negative pulse is applied to grid 58 for each successive signal (lc) applied to the system and these pulses are rectified by diode 63 and operate to actuate relay 14 in the manner already explained.

Operation of relay 1li applies direct voltage to the armature of direct current motor 88 of proper polarity to cause the motor to operate through reduction gear 8l to rotate shaft 3| in a cl'oclr.- wise direction, resulting in the rotation of potentiometers 43 and 82 in the same direction. Rotation of potentiometer 46 in aclockwise direction causes the duration of the delay pulse produced' by circuit 4l t0 increase resulting in an increase.

in duration of the negative pulse applied to grid 31 of tube 38. The duration of this pulse con.-l

tinues to increase until at a duration of 75 microseconds the tube 38 is cut off at 75 microseconds; and the negative pulse applied to grid ,68 at'that: Relay 14r4 is de-energized as a result and the rotation oftime is no longer passed by this tube.

shaft 3| ceases. Since the relationship between delay pulse duration and rotation of potentiom-Y eter 46 in circuit 4I is linear, or very nearly so,l

the shaft will have rotated through one-half its maximum travel in the clockwise direction,

corresponding to the displacement of the controly pulse to the right of its neutral position by onehalf the maximum permissible displacement. The new positions of potentiometers 48 and 82 are shown in dotted lines. The shaft 3i will remain in this position-so long as the position of the control pulse in signal (7c) is not changed;` it will also remain in this position in the absenceof a signal at terminals aX-bX-cx.

It will be noted that another result of aprogressive increase in the duration of the delay pulse from circuit 4I by rotation of shaft 3| is to cause the negative pulse applied to the grid-v tube to block passage of the negative pulse ap-V plied to its grid 86. In order to avoid hunting of the system due to this condition the negative pulse on grid 35 of tube 36 and the negative pulse on grid 31 of tube 38 are each slightly delayed by delay networks 83 and 84 respectively so that tube 36 is rendered operative slightly after the 75 microsecond point and tube 38 isv rendered inoperative slightly before the 75 micro-v second point. The resulting small interval 0f time during which both tubes are inoperative is suflicient to prevent hunting.

For operation of shaft 3i in a countercloclcwise` direction assume that the intermediate control pulse of signal (lc) is shifted back to its neutralposition so that the signal becomes the same as With this signal the negative microseconds Whereas the negative pulse applied 9 to grid3l has an initiallength of' 5 microseconds. The tube 38 consequently does not passv the pulse on grid B6 and relay 14 is not energized. How-- ever, the negative pulse applied to grid El of tube 36 now occurs initially at 75 microseconds whereas the negative pulse applied to grid 35 has a length of only 50 microseconds. Since this permits operation of tube 36 during the last 50 microseconds of the 100 microsecond interval the negative pulses on grid 6| are passed and act to operate relay 'I3 thus causing rotation of shaft 3| in a counterclockwise direction. As the shaft rotates in this direction the duration of the pulse produced by circuit 4| becomes progressively less and the negative pulse on grid 6| occurs progressively earlier until at the 50 microsecond point, which is the limit of operability of tube 35, the pulse on. grid 6| is nor longer passed and relay 13 is de-energized stopping shaft 3|. at its center position corresponding to the neutral position of the control pulse. Here again the slight delays produced by networks 82 and 84 prevent hunting by causing tube 38 to become inoperative slightly sooner than otherwise and by causing' tube 33 to become operative, due tothe progressively increasing duration of the negative pulse on grid 31, a little later than otherwise, thus insuring a short. interval in which both tubes are inoperative. The action of the circuit in producing further counterclocliwise rotation beyond the center position in response to signals of the type shown in Fig. 3 at (l) and (m) is of the same character as described above.

In the above description the neutral position of the control pulse was located at the center:

of the fixed time interval, designated by the nrst and last pulses of signal. This condition is not necessary, however, and the neutral position of the control pulse may be located at any point within the time interval. The only requirement is that when shaft 3| is in its neutral position the pulse generated by circuit 4| must be equal in duration to the time difference between the beginning of the iixed time interval. and the neutral position of the control pulse.v

It is not essential that all the control pulses in the signal shown inY Fig. 3 (-af) be used for proportional control. For example, pulses 4I and may be shifted to either side ofY their neutral position for proportional control while pulses 2 and 3 may be always maintained at their median positions and used for simple on-orf control by selectively including or excluding the pulse from the transmitted signal. In thisA case circuits of the type shown in Fig. 2 would be connected' tol terminals a3-ba-c3 and a4-b4-c4 in Fig. l, whereas simple on-oiT control circuits responsive to the presence of a pulse would be connected to terminals b1 and b2, terminals a1, c1, a2 andA c2 not being needed.

The circuit of Fig. 2 may be modied s0 that in the input signal to the circuit, as in Fig'. 3l (k) for example, the last pulse, which functions to terminate the 100 microsecond interval, is not required. This modication consistsin replacing trigger circuit 32 with any circuit capable of being triggered by the negative pulse fromV terminal as, which is: the iirst pulse of signal (le), to produce a negative pulseV of 100 microseconds duration. A delay circuit of the type shown at 4| is suitable for this purpose, Since it is not necessary that the pulse duration be continuously adjustable in this case, the diode 45 and potentiometer 4B may be dispensed with and an inverter stage 86 provided to apply a positive trigamplier and inverter 93, are the' ger pulse to grid as shown in Fig; 4. Other suitable circuits are the conventional one-cycle multivibrators such, for example, as those shown on pages 2-50 and 2-53 of the previously'mentioned book Principles of Radar. Since the design of such circuits is Well known and not a part of the invention no further discussion thereof isnecessary in this disclosure. When Fig. 2v is modied as above described thereisno need for the c terminals 0f Fig. 1 nor for the cx terminal of' Fig. 2.

In cases Where only a single control' function is desired the signal may take the form of a series of synchronizing pulses each followedbya control pulse as shown in Fig. 5. The synchronizing pulses in the figure are. designated s and' thecontroly pulses c with the center lines, which are located 50 microseconds from thesynchro-- nizing pulses, indicating* the neutral positions of-y the control pulses. The limit of' control pulse shift is again 50 microseconds on either side' of the neutral position. The separationof synchronizing pulses mustA be in excess of microseconds and is shown. in this case to be micro-- seconds. For a signal of this type a' pulse selector circuit having theA complexity of that shown inrv Fig. 1 is not required and a simpler type, such as shown inFig. 6, may beV used. In this-circuit--the signal shown in Fig. 5Y is app'liedf to gated amplier and inverter 3|! which. is normally in an op erative condition and passes the synchronizing pilse which triggers the pulse generatorl circuit 9 negative pulse which. is applied to gated ampli fier and inverter 9U rendering itv inoperative for the duration". of the: pulse andi thereby preventing passage of the later occurring control pulse. Therefore the only pulses appearing atterminal ao, which is connected to the: output of gafte'dA synchronizing' pulses s. The input signalv is4v also applied" to gated ampliiier and inverter-92 whichis-normally. biased to an. inoperative condition so that the synchro.- nizing pulse is not passed. However the 100 microsecond negative pulse generated by circuit 9| and initiated bythe synchronizing pulse is con'- verted to a positive puls-e by inverter 93 and ap plied to gated' amplifier and inverter. 92 whiz'ih it renders operative for the duration of the pulse. Control pulses lagging theY synchronizing pulses by any amount up to 100 microseconds are therefore passed by element 92` applied to terminaly bo. The pulse generator may be of any suitableA type: such as a one-cycle multivibrator orr the typeKV shown in Fig. 4. Some pulse generating circuits supply both positive and negativepulses at different points in the circuit and in such cases the inverter 33 may not be required. The terminals.` a0 and bnI of Fig. 6y are connected to terminals ax. andv bx, respectively, of. Fig; 2. Fig; 2' is of course modied in. this application by substitutingv the circuit of Fig. e, orother suitable pulse generator, for circuit 32, as alreadyv explained.

I claimv as my invention:

1. A decoding circuit for analyzing a signal of the type having a synchronizing pulse followed by a control pulse adjustable in time over a fixedinterval and about a neutral positionv within said; nxed interval, said fixed interval being Wholly sub'- sequent to said synchronizing pulse, and for causing a control mechanism having a neutral position to assume a position relative to its neutral position corresponding to the position of said control pulse relative to its neutral'position, said cir-Y cuit comprising irst and second gated'. ampliers,

This circuit generates a` 100l microsecond.

means for normally biasing said amplifiers, to an inoperative condition, means for removing said bias for the duration of said fixed interval, a delay pulse generating means containing a pulse duration adjusting means, said pulse duration` adjusting means being actuated by said control mechanism so that in the neutral position of said mechanism the duration of the delay pulse produced by said delay pulse generatingr means is equal to the time diierence between 'the start of said fixed interval and the neutral position of said control pulse and so that movement of said control mechanism to either side of its neutral position causes a linearly related increase or decrease in the duration of said delay pulse from its duration at the neutral position of the mechanism, means for initiating the pulse generating action of said delay pulse generating means at the beginning of said xed time interval, means rendering said second gatedampliiier inoperative for a'- period equal to the duration of said delay pulse, means for rendering said rst gated ampliner inoperative for a period equal to the period between the beginning of said xed interval and the occurrence of said control pulse, means for generating a sharp pulse coincident with the trailing edge oi` said delay pulse and applying same to the input of said rst gated amplifier, means for generating a sharp pulse coincident with said control pulse and applying same to the input oi said second gated amplifier, means responsive to the presence of an output signal from the first gated amplifier and the absence thereof from the secondgated amplifier to move said control mechanisrn in a delay pulse duration reducing direction, and responsive to the presence of output signal from said second gated amplifier and the absence thereof from said rst gated amplifier to move said mechanism in a delay pulse duration increasing direction.

2. Apparatus as claimed .in claim l in which delay means are provided for slightly delaying the initiation of the periods during which the two gated am-pliers are rendered inoperative with respect to the start of said fixed time interval, for the purpose of preventinghunting in the system.

.3. Apparatus as claimed in claim 2 in which means are provided for converting the movement of said control mechanism into a voltage the amplitude of which is proportional to the displacement of the mechanism from its neutral position and-the polarity of which is determined by the direction of the displacement with respect to the neutral position.

45A decoding circuit for analyzing a signal of the type having a synchronizing pulse followed by a control pulse adjustable in time over a nxed interval and about a neutral position Within said fixed interval, said fixed interval being wholly subsequent to said synchronizing pulse, and for producing a direct Voltage the amplitude of which is proportional to the displacement of the control pulse from its neutral position and the polarity of which is determined by the direction off the displacement with respect to said neutral position, said circuit comprising a potentiometer havinga movable contact, means for maintainingk a XVed-d direct voltage across said potentiometer,v a tap intermediate the ends of said potentiometer,I an output circuit connected between said movable contact and said tap, rst and second gated ainpliers, means for normally applying a disabling influence to said ampliers, means for removingsaid disabling influence for the duration of said xed interval, delay pulse generating means containing delay pulse duration adjusting means, a xed coupling between said movable Contact and said delay pulse duration adjusting means, said delay pulse duration adjusting means and said potentiometer being designed so that for zero output voltage the delay pulse duration is equal to the time dinerence between the start of said interval and the occurrence of said control pulse and for other values of output voltage the delay pulse duration is greater or less than the aforementioned duration, depending upon the polarity of the output voltage, by an amount proportional to the amplitude of the output voltage, means for initiating the pulse generating action of said delay pulse generating means at the beginning of said fixed time interval, means associated with said delay pulse generating means for rendering said second gated amplifier inoperative for a period beginning slightly after the start of said xed time interval and equal. in length to the duration of said delay pulse, means for rendering said first gatcdamplifier inoperative for a period beginning slightly after the start of said Xed time interval and equal in length to the time between the startl of said fixed time interval and the occurrence of said control pulse, means for generating a sharp pulse coincident with the trailing edge of said delay pulse and applying same to the input of said first gated amplier, means for generating a sharp pulse coincident with said control pulse and applying same to the input of said second gated amplier, and means associated with said potentiometer and the output circuits of said gated ampliiiers and responsive to the presence of output signal from said first ampliiier and the absence thereof from said second amplifier to move said movable contact in a delay pulse duration decreasing direction, and responsive to the presence of output signal from said amp-liner and the absence thereof from said rst amplifier to move said movable contact in a delay pulse duration increasing direction.

5. A decoding circuit for analyzing a signal of a type comprising first and second trigger pulses separated by a fixed time interval and a control pulse having a neutral position intermediate said trigger pulses and adjustable on either side of said neutral position over the fixed time interval defined by said trigger pulses, and for causing a control mechanism having a neutral position to assume a position relative to its neutral position corresponding to the position of said control pulse relative to its neutral position, said circuit oomprising rst, second and third trigger circuits, said trigger circuits being of the type having two amplier tubes connected in a regenerative loop whereby the circuit has two conditions of stability in each of which one of the tubes is fully conductive and the other cut orf and in which triggering of the circuit from one condition of stability to the other and then back to the iirst by two time separated trigger pulses results in the production of a rectangular pulse of duration equal to the time difference between the trigger pulses, a delay pulse generating circuit containing delay pulse duration adjusting means; means for applying said first trigger pulse to said first trigger circuit for triggering said circuit from its first to its second condition of stability, means for also applying'said first trigger pulse to said delay pulse generating circuit for initiating the generation of a delay pulse, means for producing a trigger pulse from the trailing edge `.of said delay pulse and for applying same to said f aandoen rst. trigger circuit for triggeringsaid circuit: back to its first condition ofi stability, means for applying said first-trigger pulse to said second trigger circuit for triggering said circuit from its first to its second condition of stabilitynneans for. applying said second trigger pulse to said second trigger circuit for triggering said circuitfiom its second back to its rst condition. of stability, means forapplyingV said first trigger.v pulse to said thirdy trigger circuit for triggering said circuit fromV its rst to the second conditionof stability, means for applying said control pulse tosaid third trigger circuit to trigger said circuit from itsfsecond back to its first condition of stability, a first and a second gated ampliiier, means for normally biasing said amplifiers to an inopera-tive condition, means for applying the rectangular pulse generated by saidsecond trigger circuit to said amplifiers to overcome saidbias fmfthe duration of said fixed interval, means for slightly delaying the rectangular pulse produced by said first trigger circuit and applying same to said second gated amplifier to render it. inoperative for the duration or", said pulse, means for slightly delaying the rectangular` pulse produced: by said third trigger circuit and applying same to said first gated ampliiier to render it inoperative for the .duration of said pulse, means for generating a sharp pulse from the trailing edge of said delay pulse and applying same to the input of said first gated amplifier, means for generating a sharp pulse from the trailing edge of the pulse produced by said third trigger circuit and applying same to the input of said second gated amplifier, means providing a positive coupling between said control mechanism and the `pulse duration adjusting means of said delay pulse generating means, said pulse duration adjusting means being designed and set relative to said control mechanism so that in the neutral position of said control mechanism the delay pulse duration is equal to the time interval between said first trigger pulse and said neutral position of the control pulse and so that movement of said control mechanism to either side of its neutral position causes a linearly related increase or decrease in the duration of said delay pulse from its duration at the neutral position of the mechanism, and means connected between the output circuits of said gated ampliiiers and responsive t the presence of an output signal from said first gated amplifier and the absence thereof from said second gated amplifier for causing said control mechanism to move in a delay pulse duration reducing direction and responsive to the presence of out put signal from said second gated amplifier and the absence thereof from said first gated amplifier for causing said control mechanism to move in a delay pulse duration increasing direction.

6. A ,decoding circuit for analyzing a signal of the type comprising a trigger pulse and a subsequently occurring control pulse having a neutral time position occurring within a fixed time interval measured from said trigger pulse, and for causing a control mechanism having a neutral position to assume a position relative to its neutral position corresponding to the position of said control pulse relative to its neutral position, said circuit comprising first, second and third trigger circuits, said first and third trigger circuits being of the type having two ampliiier tubes connected in a regenerative loop whereby the circuit has two conditions of stability in each of which one of the tubes is fully conductive and the other cut off and in which triggering of the 14 circuit `from one condition of stability to the other and thenback to the first, by'twotime'separated trigger pulses results' in the production' of a rectangular pulse of duration equal; to thetime difference-.between the trigger pulses; said second trigger circuity beingl a. circuit capablel upon being triggered of generating a rectangular pulse of duration equal to said xed timeinterval, a delay pulse generating circuit containing delay pulse duration adjusting means, means for applying said first trigger pulse to said rst trigger circuit for triggering said circuit from its first to its second. condition of stability, means for also applying said iirst trigger pulse` to said delaypulse generating circuit for initiating the generation of a delay'pulse', means for producing a trigger pulse fromv the trailing. edge of: said delay pulse and for.v applying same to said first trigger circuit for triggering said circuit baclr to its first condition oi stability, meansy for applying` said' first trigger pulsey to said second trigger circuit for triggering said circuit to" produce a rectangular pulse of duration equal to said iixed time interval,y means rior applying said first trigger pulse vto said third trigger circuit for triggering saiiif.

circuit from its first' to the second: condition of stability, means for applying.' said control pulse. to said third trigger circuitto trigger said circuit from its second back to its first condition of stability, a first anda second gated amplifier, means for normally biasing said amplifiers to an inoperative condition, means for applying the rectanguler pulse generated by said second trigger circuit to said amplifiers to overcome said bias for the duration of said fixed interval, means for slightly delaying the rectangular pulse produced by said first trigger circuit and applying same to said second gated amplifier to render it inoperative for the duration of said pulse, means for slightly delaying the rectangular pulse produced by said third trigger circuit and applying same to said first gated amplifier to render it inoperative for the duration of said pulse, means for generating a sharp pulse from the trailing edge of said delay pulse and applying same to the input of said first gated amplier, means for generating a sharp pulse from the trailing edge of the pulse produced by said third trigger circuit and applying same to the input of said second gated amplifier, means providing a positive coupling between said control mechanism and the pulse duration adjusting means of said delay pulse generating means, said pulse duration adjusting means being designed and set relative to said control mechanism so that in the neutral position of said control mechanism the delay pulse duration is equal to the time interval between said first trigger pulse and said neutral position of the control pulse and so that movement of said control mechanism to either side of its neutral position causes a linearly related increase or decrease in the duration of said delay pulse from its duration at the neutral position of the mechanism, and means connected between the output circuits of said gated amplifiers and responsive to the presence of an output signal from said first gated amplifier and the absence thereof from said second gated amplifier for causing said control mechanism to move in a delay pulse duration reducing direction and responsive to the presence of output signal from said second gated amplifier and the absence thereof from said rst gated amplifier for causing said control mechanism to move in a delay pulse duration increasing direction.

essere() 7. A decoding circuitfor analyzing a signal of the type having rst and second trigger pulses separated by a xed time interval and a control pulse having a neutral position intermediate said trigger pulses and adjustable on either side of said neutral position over the Xed time interval defined by said trigger pulses, and for causing a control mechanism having a neutral position to assume a position relative to its neutral position corresponding to the position of said control pulse relative to its neutral position, said circuit comprising first and second gated ampliners, means for normally applying a disabling bias to said amplifiers, means for removing said disabling bias for the time interval between said rst and second trigger pulses, means including an adjustable delay means for producing a sharp pulse occurring later than said first trigger pulse by the' amount of delay produced by said .delay means and applying said pulse to the input of said rst gated amplifier, means including. said adjustable delay means for rendering said second gated amplier inoperative for a period of time equal to the delay produced by said delay means and starting slightly after said nrst trigger pulse, means for rendering said Iirst gated amplifier inoperative for a period equal to the time difference between said rst trigger pulse and said control pulse and starting slightly later than said rst trigger pulse, means for applying a sharp 16 pulse coincident with said control pulse to the input' of said second gated amplifier, said adjustable delay means being coupled to saidl control mechanism and being so designed that said delay varies linearly with respect to movement of Asaid control mechanism and produces a delay at the neutral position of said mechanism equal to the time difference between said rst trigger pulse and said neutral position of the control pulse, and means coupling the output circuits of said gated amplifiers to said control mechanism and responsive to the presence of output signal from said first amplifier and the absence thereof from said second amplifier to cause movement of said control mechanism in a delay decreasing direction and responsive to the presence of output signal from said second amplifier and the absence thereof from said first amplifier to cause movement of said mechanism in a delay increasing direction.

CHESTER I. SCHAFER.

REFERENCES CITED UNITED STATES PATENTS Name Date Hollingsworth Dec. 30, 194.7

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